Polymer gels possess a number of interesting properties which solids or liquids cannot singly have, such as low surface friction property, permeability for materials and organism-like positive motorial property against external stimulations. When an attempt is made to utilize such gels for daily life or in the medical and industrial fields, exploiting such properties, however, most of them currently lack mechanical strength and are brittle, apart from some of them such as polyvinyl alcohol (PVA) and poly-2-hydroxyethyl methacrylate (PHEMA) gels. If a gel (hydrogel, in particular) possessing a high strength were produced and if the principles thereof were understood and the mechanical strength of thereof were freely controlled, highly functional biomaterials could be developed at a practical level not only for livelihood and industrial utilizations but as well for applications in artificial blood vessels exploiting the permeability for materials of the gels and artificial arthrodial cartilages of gels having low-friction surfaces, with an expectation that the values of use of the polymer gels would drastically be increased.
Accordingly, this invention aims to provide a hydrogel having a high content of water and an excellent mechanical strength while exploiting the characteristics of a gel for retaining shapes.